Magnetron

The Magnetron consists of two magnet rotors mounted on a wooden base. If you spin one of the rotors, you will immediately see the other rotor moving, as the two sets of magnets interact.

Even more interesting effects can be seen if you place two or more Magnetrons together on a flat surface, and spin one of the rotors. All of the other rotors will turn, but not at the same time, and not always in the same direction. One particular rotor can be completely still at one moment, then rotate clockwise, and then later it can rotate anti-clockwise.

It is not possible to predict which rotors will be moving and in which direction, for any time in the future, and for that reason this system is said to exhibit chaotic motion.